It's not totally accurate, but for quick and dirty genny testing you can hook up a bank of high wattage devices. A couple of portable heaters, heat guns, hair dryers, whatever. Tally up the total wattage. You can let them run for hours if needed. A multimeter with an AC clamp can accurately measure amperage output, but youll have to separate the output leads at the genny. A foot-long extension cord made of three separate pieces of wire can be made to accomplish this.
The genny also needs to put out the correct frequency, as some electronics may be sensitive. An inverter generator should take care of this, I think. Pretty sure your Honda is an inverter generator. Can anyone verify?
Banging, bouncing, and vibration can do a number on unhardened electronics. Sitting stationary in a house is a hell of a lot nicer than riding in a vehicle.